Magnetic films of various compositions have been developed for different applications. For example, permanent magnet films may be used in magnetic recording systems. However, conventional permanent magnet films do not typically possess a satisfactory combination of high magnetic coercivity (Hc) and high remnant magnetization (Mr) at thicknesses that yield sufficiently high magnetic fields for use in applications such as stabilization of magnetic sensors.
The types of sensors typically used today for magnetic recording are categorized as current-in-plane (CIP) sensors. In CIP sensors, the current flows parallel to the plane of stacked films in the sensor. One possible sensor type for future high density recording is the current perpendicular to the plane (CPP) sensor. In CPP designs, the current flows perpendicular to the plane of the stacked films.
The CPP sensors are of interest because of their potentially larger giant magnetoresistance (GMR) or change in resistance when a magnetic field is applied. The larger GMR comes about because all of the current needs to pass through every ferromagnetic/non-magnetic/ferromagnetic (FM/NM/FM) series of interfaces and none of the current is shunted around the interfaces. Since every film and interface leads to additional resistance, it is desired to have all of the films and interfaces contribute to the overall change in resistance. A GMR multilayer consists of a series of FM/NM bilayers. Every series of interfaces provides an opportunity for interfacial spin-dependent scattering and every ferromagnetic material provides an opportunity for bulk spin-dependent bulk.
CPP GMR multilayer sensors may be biased by a permanent magnet adjacent to the stacked films in order to orient magnetizations of adjacent ferromagnetic layers in the desired directions. However, currently available permanent magnet materials do not possess optimal properties such as high Hc and high Mr at sufficient film thicknesses to provide adequate biasing magnetic fields.
The present invention has been developed in view of the foregoing and to address other deficiencies of the prior art.